Method of making stainless-clad sheet steel



June 30, 1942. H. w. DODSON ETAL 2,288,184

METHOD 0? MAKING sumwsswmn SHEET-STEEL Filed April 7, 1939 INVENTOR..Efoward ED003011 Patented June 30, 1942 METHOD OF MAKING STAINLESS-GLADSHEET STEEL Howard W. Dodson and David G. Neuman,

Philadelphia, Pa.

Application April 7, 1939, Serial No. 266,607

1 Claim.

The present invention relates to a certain new and useful method ofmaking stainless clad steel, although the method of the presentinvention may be applied to any other composite sheet metal formed oftwo pie-formed sheets of metal.

Stainless steel is now well recognized in the art, and for the variouscompositions or analyses and for the various methods of making stainlesssteel reference may be had to the known and published art. 1

Stainless steel is an expensive metal compared to the more commonferrous metals, such as structural steel, or ordinary sheet steel ofvarious grades and analyses, and for this reason stainless steel is moreor less limited in its uses by economic considerations. For this reason,various attempts have been made to make what is sometimes referred to asarmored stainless steel sheets wherein some part of the total thicknessof the sheet would be ordinary steel of suitable grade and some otherpart of the thickness would be stainless steel, so that the sheetwillpresent a stainless steel surface on one side and an ordinarysteel-surface of the other side. Such armored stainless steel sheetswereintended wherever stainless steel surface was desired, but

where the tensile strength of stainless steel was not necessary, thatis, where a stainless steel 7 Was not used for structural strength butlargely for corrosion resistance, and where an ordinary steel wouldamply serve for structural strength.

One of the practices in the past has been to make an ingot of a suitablestainless steel alloy and another ingot of anordinary steel of suitablegrade, as for instance soft steel, both ingots being the same size.placed one on top of the other while hot and plastic, and the two ingotswere then rolled together through rapid rolling operations until theunited ingots were thinned down and spread out into a single two-plysheet in much the same way as that in which ordinary sheet metal isrolled. As the two ingots are flattened out in successive rollingoperations they are also firmly united with each other. One of thedifficulties encountered by this process has been a comparative lack ofuniformity because of the difference in plasticity of the two nigots andtherefore the difference in yield under the rolling operation. Thisprocess has been unable to produce comparatively thin two-ply armoredstainless steel sheets.

One'of the objects of the present invention These two ingots were then 7and which will be much thinner and hence suitable for many purposes forwhich a thick sheet is not suitable, and which will be more uniform inthe thicknesses of the two different metal layers.

In the accompanying drawing in which like reference characters indicatelike parts,

Figure 1 represents a diagrammatic view of apparatus for carrying outthe present invention;

Figure 2 represents a similar diagrammatic View of a modified form ofapparatus.

Figure 3 represents a diagrammatic perspective view of the weldingrolls.

According to the present invention, a preformed sheet 5 of stainlesssteel alloy and a preformed sheet 6 of any suitable carbon steel areprovided, preferably supplied from corresponding coiled-up supplies Iand 8 coiled up on suitable supply rolls 8 and ill. The sheets 5 and 6may be of any suitable thickness and may indeed be quite thin, runningdown to small fractions of an inch. Thus, the stainless steel sheet 5may be five or ten thousandths of an inch, while the backing steel sheet6 may be of any desired thickness depending on the structural strengthdesired in the resultant two-ply sheet I I.

The sheets 5 and 6 may be of any suitable width depending on the currentavailable and the capacity of the machine.

The sheets 5 and 6 are fed from the rolls 9 and ID in superposedpositions as indicated in the general manner shown in Figure 1, tobetween a pair of juxtaposed welding rolls l2 and I3 mounted inelectrically insulated housings and suitably journalled and havingconnected to them the opposite terminals of an electrical circuit asindicated in the drawing. Suitable backing rolls l4 and I5 serve topress against the respective welding rolls i2 and I3 and to maintain thepressure therebetween. The welding rolls l2 and i3 are electricallyinsulated with respect to each other so that current must pass throughthe sheets 5 and 6.

By passing either a continuous but preferably a series of intermittentelectrical charges of suitable voltage and amperage and for suitableperiods through the rolls l2 and I3, and hence the sheets 5 and 6, thesesheets are welded to each other as indicated in Figure 3, the resistanceof the sheets 5 and '6 serving to produce heat therein. When usingintermittent or individual electrical charges, the successive electricalcharges are so timed in relation to the rotation of the rolls l2 and I3and in relation to the linear speed of the sheets 5 and 6 that the weldproduced by one electrical charge passing through the sheets will beslightly overlapped by the next weld produced by the next electricalcharge passing through the sheets, and so on, so that the net efl'ectwill be a generally continuous weld between the sheets.

The sheets may either be wound directly upon a take-up roll [6 afterthey leave the welding rolls l2 and 13, or they may be first passedthrough one ormore sets of rolls like I! and I8 backed by suitablebacking rolls i9 and 20, which serve as a strip mill to reduce theover-all thickness of the composite two ply sheet II to any desiredextent. This reduction may be only slight or it may be substantialdepending on the desired result.

The sheets and 6 are cleaned preliminary to the process hereinaboveindicated, by any suitable pickling or cleaning methods, so that thejuncture surfaces 2| and 22 thereof are clean and conducive toproduction of a good wel juncture or union.

Thus, the surfaces 2| and 22 must be entirely free of scale or othersurface formations.

All the rolls, including the supply rolls 9 and Ill and take-up roll,etc., as well as the welding rolls and strip mill rolls, are suitablyjournalled in bearings supported by housings in the manner similar tothat employed in rolling mills, and these parts are not here shownbecause they may be of any desired construction indicated by goodengineering practice applicable to rolling mills.

The working rolls or welding rolls I2 and I3 are made of metal havinghigh electrical con-- ductivity and maximum hardness. Such materials arenow known and used as electrodes in resistance welding methods known inthe art. These rolls'l2 and I3 may be suitably cooled by water or othermeansso as to reduce or minimize the heat efiect thereon by reason ofthe welding operation.

The present method permitsfine reduction in the thickness of thecomposite or two-ply stainless clad sheet steel, without creating workhardness. It also eliminates or minimizes work hardness already created.The welding heat being accurately controllable acts as an annealingagent. For this reason the method of the present invention permitsrolling lighter gauges than heretofore commercially practicable. Thepresent invention also permits a stainless clad steel product at lowercost thereby allowing such composite two-ply sheet metal to enter fieldsnot now using stainless steel because of cost, such as for instance acidand chemical tanks; liquid storage and transportation tanks in general;barrels; water piping; building construction; structural work and thelike. I

The pressure used between the welding rolls l2 and B may be increased soas to assistin the reduction of the thickness, thereby relieving some ofthe work to be done by the rolls l1 and I8 or other successive pairs ofrolls of the same kind.

The process or method of the present invention is readily adaptable tocontinuous mill operations or continuous mill line-up, entailing littleor no substantial changes to other machinery or processes.

By the present method also any strips which have been rejected asimperfect or otherwise deficient for commercial use may be built up andre-processed.

The amount of current and therefore the heat may be controlled and alsothe time interval during which each passage of current is permitted toflow through the metal.

By the present process or method, sheets of various gauges and analysesmay be readily assembled on short notice and without detailedscheduling. Thus, the relative thickness of the stainless steel alloysheet and the ordinary sheet steel may be varied, and the analysis orquality ofthe stainless steel and regular steel may also be varied.Thus, by merely carrying in stock stainless steel sheets ofrelativelyfew thicknesses or gauges and of relatively few compositions oranalyses, and by carrying in stock an assortment of ordinary ,steelsheetmetal of various gauges and analyses,. any two sheets may readily becombined to produce a composite two-ply stainless steel clad sheethaving any desired over-all thickness and having any desired thicknessof stainless steel alloy and regular steel and having any desiredanalyses in either of the two plies.

As hereinabove pointed out, the time interval during which each chargeof current is passed through is correlated to the speed at which therolls rotate or the linear speeds of the sheets. If desired, however,the rotation of the rolls l2 and I3 and the movement of the sheets atthe welding point may be made intermittent with the motion timed inrelation to the passage of current so that with each/passage of currentthe sheets maybe stationary forthe duration of the current-passage afterwhich thesheets are moved a slight amount for the passage of the nextcharge of current and so forth. This may not be necessary, however,because the rotation of the rolls I2 and I3 and the linear motion of thesheets 5 and 6 at the welding points may be continuous. If, however, anintermittent motion is used at that point, the operation of the one ormore sets of strip mill rolls may nevertheless be continuous, dueallowance being made for allowing a slight slack between the rolls I1and I8 and the rolls l2 and I3; this slack being made up by any suitablevariable or yieldable tensioning device which will maintain the more orless uniform tension notwithstanding the intermittent motion of therolls l2 and I3 and the continuous motion of the rolls I1 and I8.

The term ordinary steel where used in the following claim has referenceto steel other than the stainless steel used in making up the twoplysheet.

The present invention may be embodied in not restrictive, referencebeing had-to the appended claim rather than to the foregoing descriptionto indicate the scope of the invention.

Having thus described the invention, what is hereby claimed as new anddesired to be secured by Letters Patent, is:

A generally continuous method of making twoply stainless-cladsheet-steel, which comprises bringing together a preformed relativelythin and relatively wide sheet of stainless steel-alloy and a pro-formedsheet of ordinary steel of generally like width, along a line across thesheets, exerting pressure upon said sheets simultaneously to press saidsheets together on said line while the widths of said sheets are insubstantial registration with each other along said line ofpressedcontact, continuously moving successive portions of said sheetsinto said pressed-line contact in a direction transversely of said line,and intersaid two sheets together substantially continumlttently passinga welding electrical current through said two sheets throughsubstantially the entire line of pressed-contact as successive portionsof said sheets are moved into said pressed-line contact, of an intensityand volume and for a sufllcient length of time in relation to the speedof the motion of said sheets to weld 5 said sheets.

ously throughout their contiguous major surfaces by closely-spacedgenerally parallel line-welds, each formed simultaneously across thewidth of HOWARD W. DODSON. DAVID G. NEUMAN.

